Cardiovascular diseases, for example ischemic heart diseases, cerebrovascular diseases, atherosclerosis and hypertension, together with malignant tumors, are quite important diseases as major causes of death. Among these cardiovascular diseases, ischemic heart diseases and insufficiency of cerebral or peripheral circulation are generally understood to be caused by a lack of nutrition and oxygen supply, which is originally caused by insufficient blood flow resulting from arterial thrombus formation or from atherosclerosis. Therefore, the kind of drug which improves blood flow of the affected organ based on vasodilating action on the ischemic area, such as coronary arteries, is effective in the treatment of these diseases. Also, the kind of drug that inhibits platelet aggregation, which is a cause of arterial thrombus formation, or drug that reduces elevated serum cholesterol, which causes atherosclerosis, is understood to be effective in preventing pathogenesis of these diseasess.
Vasodilators, for example hydralazine, show hypotensive activity and have been frequently used in the treatment of hypertensive disorders. Recently, vasodilators have also been used in the treatment of cardiac insufficiency, based on their action to reduce peripheral vascular resistance, as reported by Kei Itoh et al. (Nippon Rinsho, 36(11)51(1978)) and by Shinobu Matsui et al. (Abstract No.165, The 43rd annual congress of the Japanese Circulation Society).